2025 MLB POSTOFF: Factor X para los 8 equipos para lograr ALDS, NLLDS

We now know who has made it to the divisional round of the MLB postseason and who the biggest stars are.

That said, which players could make or break their respective team’s World Series aspirations?

Here’s the X factor for each of the eight teams that cracked the MLB Divisional Series, mentioned in order of seeding, beginning with the American League:

Despite earning a first-round bye, Toronto’s starting rotation, which was 20th in the regular season with a 4.34 ERA, remains a question mark. Its trade-deadline acquisition of Bieber from the Cleveland Guardians could change the tide.

Bieber, who hadn’t pitched in an MLB game since April 2024 due to an elbow injury, made his Blue Jays debut on August 22 and has been sharp to date. In seven starts (40 1/3 innings pitched), the 2020 AL Cy Young Award winner has posted a 3.57 ERA, 1.02 WHIP, held opponents to a .225 batting average and done so with a consistent, five-pitch arsenal (four-seamer, slider, knuckle curveball, changeup and cutter).

Kevin Gausman and Chris Bassitt are having plausible seasons, but Max Scherzer was hit hard down the home stretch of the regular season, and Jose Berrios was recently moved to the bullpen. Bieber is Toronto’s best chance at a third starter who can pitch a third time through the order. When healthy and at his best, the right-hander induces weak contact and pitches deep into games. Bieber building on an auspicious regular season is paramount to take stress off the Blue Jays’ bullpen and complement a humming offense, which was first in hits and fourth in runs this season.

Can Seattle’s starting rotation be four deep? That’s how Kirby can make a difference.

Seattle’s identity for the past five years has been great starting pitching. This year, the Mariners’ offense has been ahead of their rotation. Granted, its starting staff, which was tied for 13th in MLB with a 3.97 ERA, more than holds its own. Kirby has been respectable this season, but he still posted a career-high 4.21 ERA, with opponents hitting .252 off the right-hander. Bryan Woo, Logan Gilbert and Luis Castillo have been Seattle’s top three arms, as expected, and it could be those arms whom manager Dan Wilson heavily relies on to get through the ALDS. That said, a deeper postseason run will require more rotation length, with Kirby, who posts strikeouts at a high clip, being a prime candidate to pick up the pace.

Kirby, who surrendered just two combined runs in his past two starts, even pitching through the fifth inning would allow manager Wilson to protect his bullpen so that he doesn’t have to mull deploying another member of his rotation earlier in the game. Essentially, avoiding a de facto bullpen day. 

The Yankees led the majors in home runs and their starting rotation looks strong, especially after Cam Schlittler‘s eight shutout innings in Game 3 of the Wild Card Series. The biggest key for New York getting back to the World Series? Its bullpen, which was 23rd in the sport with a 4.37 ERA, shutting the door. Enter Dream Weaver.

One year ago, Weaver was one of the best relievers in the sport. He was consistently keeping runners off the base paths, getting hitters to walk back to the dugout in quick order and became the Yankees’ closer. Weaver posted a 1.76 ERA and four saves in 15 1/3 innings in the 2024 postseason. This season has been a mixed bag for Weaver, who, at times, has been dominant but other times been ambushed. For instance, in Game 1 of the Wild Card Series, Weaver, who led Yankees relievers with 10 home runs given up in the regular season, surrendered three consecutive baserunners without getting an out in the seventh inning of an eventual loss.

David Bednar has been superb, while Devin Williams and Camilo Doval have been seesaws, but Weaver is the reliever with the most upside in New York’s bullpen. A shutdown Weaver helps the Yankees close out narrow victories, similar to the ones they had in the Wild Card Series, a round that saw New York score just three runs per game.

At face value, Detroit’s identity is its starting rotation. Remove likely back-to-back AL Cy Young Award winner Tarik Skubal from the equation, though, and what is this rotation in the present? The best version of Flaherty would solidify this aspect of their club.

At his best, Flaherty is an electric, top-of-the-rotation force who strikes out hitters at a high rate and provides length. That said, he has struggled to repeat a great season, partially due to injury, and this year has been a setback. After a 2024 campaign that saw him post a 3.17 ERA and 1.07 WHIP, the right-hander posted a 4.64 ERA and 1.28 WHIP this season. Let’s take Flaherty’s 2024 postseason with the Los Angeles Dodgers into account. He followed up a rocky, 5 1/3-inning outing by tossing seven scoreless innings in Game 1 of the NLCS. After that? He gave up eight runs in three innings, followed by a plausible, 5 1/3-inning outing, which was then followed by Flaherty not escaping the second inning in his final outing of the postseason.

When Flaherty is on and finding success with his off-speed pitches, he’s an ace. If he’s hit hard early, the right-hander gets pulled in quick order. Which version of Flaherty Detroit gets is pivotal.

This may be the best team the Brewers have sported in the 21st century. Whether they actually break through, though, is dependent on the same factor that has sent them home in the postseason in recent memory: can they get enough offense? Milwaukee can look to Vaughn for the boom.

Since debuting with the Brewers in July after a trade with the Chicago White Sox earlier in the year, Vaughn has been an indispensable source of offense. Serving as their primary first baseman, Vaughn has totaled nine home runs and 46 RBIs in 64 games, while posting a .308/.375/.493 slash line. Vaughn has possessed a great deal of power throughout his career, ranking in the upper-quarter of the sport in average exit velocity (84%), hard-hit percentage (79%) and barrel percentage (75%) this season.

Can Vaughn keep up the production? Yes, Milwaukee was second in on-base percentage and third in runs and hits. At the same time, it was 22nd in home runs, and this is a slug-fest sport. If the Brewers are sent home early, it won’t be because of their stellar starting pitching or stealthy bullpen: it will be because of a lack of slugging.

The Phillies managed to win the NL East and earn a first-round bye despite losing ace Zack Wheeler for the season in August. At the same time, somebody in their starting rotation will have to take it to the next level this fall, and Nola is the top candidate to do so.

To put it kindly, this has been a bad year for Nola, who posted a 6.01 ERA and surrendered 18 home runs in 17 regular-season starts. The veteran right-hander, who gave up just one run and two baserunners over eight innings in his last outing, is better than this. Nola, who has made 10 career postseason starts, can make hitters whiff at his knuckle curveball, throw deep into games and be a rotation anchor.

Cristopher Sanchez (2.50 ERA and 212 strikeouts in 32 starts) is having a breakout season; Ranger Suarez is healthy and rocking; Jesus Luzardo is having an encouraging 2025 campaign; get the best version of Nola, and the Phillies’ rotation can go toe-to-toe with any in the sport.

Apparently, a $350 million payroll can’t ensure a top-10 bullpen. In fact, the Dodgers’ rank in the bottom-third of the sport in bullpen ERA, sporting a 4.27 ERA, which is tied for 20th in MLB. Their biggest offseason addition to the bullpen, Scott (four-year, $72 million deal), has struggled but has been here before and could be a game-changer in the coming weeks.

This season, Scott has posted a 4.74 ERA, blown an MLB-high 10 saves and opponents are hitting .254 against him. It was just one year ago when the southpaw was an All-Star in a season split between the Miami Marlins and San Diego Padres that saw him pitch 4 1/3 scoreless innings in the postseason.

If the Dodgers get the Scott they signed up for, they get an elite, left-handed arm to deploy in the late innings. If Scott, who primarily — if not entirely — deploys a four-seamer and slider, continues to get hit hard and/or loses the faith of manager Dave Roberts, their hopes of repeating as World Series champions could end up being even more reliant on their starting rotation dominating. 

The Cubs have an offense that can mash. Their 2025 postseason success is dependent on their rotation coming into its own, and Imanaga is pivotal for Chicago because of how managerial tendencies change this late in the year.

For the first three months of the season, Imanaga was exceptional. However, over his last 12 starts, hard-contact outs caught up to Imanaga, as the left-hander recorded a 5.17 ERA and gave up 20 home runs during that span. If Imanaga, who one could argue is Chicago’s most talented starting pitcher but has never made an MLB postseason start and can heavily rely on his four-seamer, gets in trouble in the early going, it forces manager Craig Counsell’s hand.

Moreover, going up against a Brewers team that prides itself on starting pitching and defense, the Cubs can’t afford to be going to their bullpen in the second or third inning in a series that likely will be a low-scoring affair should Chicago pull off the upset. A sharp Imanaga takes a should-be competitive series down to the wire. An Imanaga that labors and forces an early pitching change puts Chicago behind the eight-ball.

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